Invasive alien species (IAS) are one of the major drivers of change that can negatively affect biodiversity, ecosystem functions and services and human health; islands are particularly vulnerable to biological invasions. Horizon scanning can lead to prioritisation of IAS to inform decision-making and action; its scale and scope can vary depending on the need. We focussed on IAS likely to arrive, establish and affect biodiversity and human health on the Mediterranean island of Cyprus. The scope of the horizon scanning was the entire island of Cyprus. We used a two-step consensus-building process in which experts reviewed and scored lists of alien species on their likelihood of arrival, establishment and potential to affect biodiversity, ecosystems and/or human health in the next 10 years. We reviewed 225 alien species, considered to be currently absent on Cyprus, across taxa and environments. We agreed upon 100 species that constituted very high, high or medium biodiversity risk, often arriving through multiple pathways of introduction. The remaining 125 species were ranked as low risk. The potential impacts on human health were documented for all 225 species; 82 species were considered to have a potentially negative impact on human health ranging from nuisance to disease transmission. The scope of the horizon scanning was the entire island of Cyprus, but the thematic groups also considered the relevance of the top 100 species to the Sovereign Base Areas of Cyprus, given their differing governance. This horizon scan provides the first systematic exercise to identify invasive alien species of potential concern to biodiversity and ecosystems but also human health within the Mediterranean region. The process and outcomes should provide other islands in the region and beyond with baseline data to improve IAS prioritisation and management.

Stickleback fishes in the family Gasterosteidae have become model organisms in ecology and evolutionary biology. However, even in the case of the most widely studied species in this family - the three-spined stickleback (Gasterosteus aculeatus) - the worldwide phylogenetic relationships and colonization history of the different populations and lineages remain poorly resolved. Using a large collection of samples covering most parts of the species distribution range, we subjected thousands of single nucleotide polymorphisms to coalescent analyses in order to reconstruct a robust worldwide phylogeny of extant G. aculeatus populations, as well as their ancestral geographic distributions using Statistical-Dispersal Vicariance and Bayesian Binary MCMC analyses. The results suggest that contemporary populations originated from the Pacific Ocean in the Late Pleistocene, and the Atlantic was colonized through the Arctic Ocean by a lineage that diverged from Pacific sticklebacks ca 44.6 Kya. This lineage contains two branches: one that is distributed in the Mediterranean area, from the Iberian Peninsula to the Black Sea ('Southern European Clade'), and another that is comprised of populations from northern Europe and the east coast of North America ('Trans-Atlantic Clade'). Hence, the results suggest that the North American East Coast was colonized by trans-Atlantic migration. Coalescence-based divergence time estimates suggest that divergence among major clades is much more recent than previously estimated.